The Adaptive Immune Response Flashcards

Flashcards covering B cell and antibody diversity, function, and development, based on lecture notes from Deborah Dunn-Walters.

Adaptive Immune System Principle

Start with a diverse repertoire to match pathogens, expand the matched cell, maintain matched cells for future memory.

T cell receptor

Membrane bound receptor that recognizes peptide antigen presented by MHC on other cells.

B cell receptor

Membrane bound or soluble (as ANTIBODY) receptor that recognizes whole antigens and can be different isotypes.

Antibody Function: Neutralization

Blocks interaction of toxins and viruses with cells.

Antibody Function: Opsonization

Promotes phagocytosis and killing activity by other cells.

Antibody Function: Complement Activation

Helps kill pathogens via the complement cascade.

Antibody Function: Agglutination

Agglutinates particles such as pathogen debris and viruses.

Antibody Function: ADCC

Mediates Antibody Dependent Cell-Mediated Cytotoxicity.

Location of B cell Development

Bone Marrow

Location of T cell Development

Thymus

Antigen Specificity

Determined by the variable region of the antibody with two binding sites.

Antibody Class

Determined by the constant region (Fc region) of the antibody, influencing its function.

Gene Rearrangement Enzymes

RAG1 and RAG2 (Recombination Activating Genes)

Heavy Chain Gene Segments

V, D, and J segments

Light Chain Gene Segments

V and J segments

Junctional Diversity

Diversity created at the junctions of gene segments by nucleotide removal or insertion, facilitated by TdT.

Activation Induced Cytidine Deaminase (AID)

Enzyme required for hypermutation and class switching in B cells within the germinal center.

T helper (Th2) cells

Provide help to B cells through cytokines and contact in the germinal center.

Class Switching

Switching the class (and therefore function) of the antibody while keeping the antigen specificity in the variable region.

IgD Function

Membrane-bound immunoglobulin found on naive B cells.

IgM Characteristics

Default immunoglobulin that B cells start with; forms pentamers and efficiently activates complement.

IgG Characteristics

Main antibody secreted into blood after class switching; good at opsonization and ADCC.

IgA Characteristics

Mucosal antibody produced at mucosal surfaces and secreted into breast milk; can form a dimer.

IgE Characteristics

Important in parasitic infection and allergy; binds to mast cells and causes degranulation upon antigen cross-linking.

Somatic Hypermutation

Deliberate mutation of Ig genes, starting with enzyme AID at hotspots in the germinal center.

T-independent type I (TI-I) antigens

Polyclonal activators that activate B cells without needing a specific receptor (e.g., via TLRs).

T-independent type II (TI-II) antigens

Large molecules with repeating determinants that cross-link multiple receptors on the B cell surface.

T-dependent (TD) antigens

Protein antigens that require T cell help for B cell activation and memory B cell formation.

CD40-CD40L interaction

Signal 2 provided by T cells to B cells, promoting B cell proliferation, differentiation, isotype switching, and germinal center development.

Germinal Center

Specialized microenvironment where hypermutation and class switching occur, requiring AID enzyme and T cell help.